Gas detector



. O. HEIL Oct. 1l, 1960 GAS DETECTOR Filed April 4, 1958 f f 5 7' CHI/766B 2,956,224 oAs DETECTOR oskar Heil, 1775 Parrott' Drive, san Mateo, Fil-edY Apr. 4, 1956, Ser; 726,559

6 claims. (cl. szass) (Granted under Title as, Uls. desde dsir, see. 266') The inv'ention described herein n tay bernanufacturd and used by er for the United States Government for governmental purposes without payment to` me of any royalty thereon.

This invention relates to' a device for" sensing the presence of a gas.

One' object of this invention is Ato provide device fo use as a` vacuum' gauge for measuring the residual gas within a container.

Another object is to provide a device whieli b'e used as a leak detector and which will detect a gas' such as helium, used as a tracer gas.

These and other objects' will be hiere' fully niiderstdd from the following description taken with the di'yir'ig wherein:

Fig. 1 is a diagrammatic illustration of a gas detector according to the invention.

Fig. 2 is a diagrammatic illustration showing the potential distribution for the electrode system of the gas detector of Fig.v 1.

Referring more particularly Ato the drawing, the gas detector 10 has an envelope 11, er' cathode 12, a gas ionizing region 13, a repeller grid 14 and a collctof 15. The gas ionizing region 13 has a first pair of electrodes 16, a second pair 17 and a third pair 18. The gas ionizing region is separated from the rest of the tube by means of an inclosure 19 to produce an ionizing chamber. The region of the tube `outside of the gas ionizing chamber is kept at a high vacuum by means of a pump 20. A passage 21 is provided between the chamber 25 under test and the region 13. lf the vacuum in chamber 25 is not near that in tube 10, a pressure differential valve can be provided in passage 21. An axial magnetic eld is provided by means of a magnetic circuit as indicated by the pole pieces 22 and 23. The potential distribution on the electrodes is as shown in Fig. 2. The potential distribution between electrodes 16 and 18 is substantially a parabolic potential distribution. A frequency source 24 is connected in the circuit between electrodes 16 and 18. It is to be understood that other circuit connections between the frequency source and the electrode system could be used if desired.

In the operation of the device of Fig. 1, the electrons emitted by the cathodes 12 are accelerated by electrodes 16, retarded by electrodes 17, accelerated by electrode 18 and forced to return by electrode 14. At the other end of their travel, these electrons are repelled by the cathode so that they make multiple transits through the electrode system and finally end up on electrodes 16 and 18.

2,956,224Y Patented oet. 11, 1960 2, is highest hear electrode 17 forms' a potential groove fo'rV the ions, thereby preventing them front feaeliing electrode 17, and therefore causes the ions to 'continue their oscillating motion. The magnetic Held guidesl the leitIO'liSv Ii their path SO that the lf leli BWC''S as a guide for the oscillating iefis. A signal at the iii resonant frequency of the ions within chamber 25 is applied between electrodes 16 and 18 by iiie'an's of a frequency source 24. Resonating ionsV will their piek up energy and will be thrown out beyond electde 14 where they can be collected by electrode 15 tov podlie an yc'intpu't signal. These ions will not be tbiow out toward the cathode since the' positive potential 'ols l'- trode 16 is greater than the potential onelctxro'de 1'8.

When the device is used as a vaeuurii gauge', the signal' level in the output can be' used to indicate tli dg of vacuum.

When' the device iS Sed as le'k detector', aline ply of helium is directed against and movedv ovi' the siifaee `of the chamber 25 and an' output from the lkdefetr will thus indicate the position f the leali;

There is thus provided a devi wliih Be s'd to detect very small quantities of gas within a chain eri.

while ene specie@ embediiiieiit has heefi described in detail, it is obvious that numerous changes' n'iy be' "de Without departing from the general p'lir'ic'ig'llesv p of the invention.

l claim:

I. A device for detecting the presence of a g prising: an electrn' tube envelope, a gas iol chamber within said envelope, means for directing a beam of electrons alonga path within 'said ionization chamber, means for producing praholie ptentilv .with said beam path, an output means connected to said collector electrode.

2. A device for detecting the presence of a gas comprising: an electron tube envelope, a gas ionization chamber within said envelope, means for directing a beam of electrons along a path within said ionization chamber, means for producing a parabolic potential field distribution along said path within said chamber, means for admitting gas to said chamber, means for maintaining a -vacuum in the portion of said envelope outside `of said chamber, means for causing said electrons to make multiple transits through said chamber to thereby ionize the gas within said chamber, means for providing an axial magnetic eld within said chamber to thereby cause said electrons to act as a guide for the ions, means to apply a signal at the ion resonant frequency to said chamber adjacent said lbeam path to supply energy to the ions within said chamber, an ion collector electrode beyond and coaxial with said beam path, an output means connected to said collector electrode.

3. A device for detecting the presence of a gas comprising: a tube envelope, a vacuum pump connected to said envelope, a gas ionization chamber within said envelope, means for admitting said gas to said ionization chamber, means for directing a beam of electrons through said chamber, means for producing a parabolic potential field distribution within said chamber, a repeller electrode, means for establishing a repeller Voltage on said beam producing means and said repeller electrode, means Vfor providing an axial magnetic field within said chamber,

a collector electrode adjacent said repeller electrode and located on the side of said repeller electrode remote from said chamber, means for producing a signal at the'ion resonant frequency of said gas, means for coupling said signal to the ions Within said ionizing chamber to thereby cause said ions to overcome the repelling iield of said repeller electrode and thereby reach said collector electrode and an output means connected to said collector electrode.

4. A device for detecting the presence of a gas cornprsing: an envelope, an ionization chamber within said envelope, a rst pair of electrodes at one end of said chamber, a second pair of electrodes at the other end of said chamber and a third pair of electrodes located Within said chamber between said irst set of electrodes and 'said second set of electrodes, means connected to saidv electrodes for producing a parabolic potential field distribution within said chamber, means for admitting said gas to said ionization chamber, means for maintaining a vacuum in the portion of said envelope outside of said chamber, means including a cathode for directing a beam of electrons through said chamber, a signal source, means for coupling said signal source between said rst and said second pair of electrodes, a repeller electrode, means for applying an electron repelling voltage to said cathode and said repeller electrode, means for applying an axial magnetic field Within said chamber, a collector electrode adjacent said repeller electrode and located on the side thereof remote from said chamber, a vacuum pump connected to said envelope for maintaining a vacuum within said envelope in the region outside of said ionization chamber and an output connected to said collector electrode.

5. A gas leak detector comprising: a tube envelope, a

-gas ionizing chamber within said envelope, means for admitting said gas to said ionizing chamber, means for maintaining a vacuum in the portion of said envelope outside of said chamber, means including a cathode for directing a beam of electrons through said chamber, a

first, second and third pair of electrodes longitudinally displaced along the beam path, means connected to said electrode pairs for producing a parabolic potential field distribution Within said chamber, a repeller electrode, means for applying an electron repelling voltage to said cathode and to said repeller electrode, means for providing an axial magnetic eld within said chamber, means for producing a signal at the ion resonant frequency of said gas, means for applying said signal to at least one of said pairs of electrodes, a collector electrode adjacent said repeller electrode and on the side thereof remote from said chamber and an output means connected to said collector electrode.

6. A vacuum gauge comprising: an envelope, a gas ionization chamber within said envelope, a rst pair of electrodes at one end of said chamber, a second pair of electrodes at the other end of said chamber and a third pair of electrodes locatedl Within lsaid chamber between said rst pair of electrodes and said second pair of electrodes, means for admittingV gas from a chamber under test to Said ionization chamber, means for maintaining a vacuum in the portion of said envelope outside of said ionization chamber, means for directing a beam of electrons through said ionization chamber, means for producing a parabolic potential field distribution within said chamber, a repeller electrode, means for providing a repeller voltage on said cathode and said repeller electrode, means for providing an axial magnetic eld within said chamber, means for producing a signal at the ion resonant frequency of said gas within said chamber, means for applying said signal between said rst and said second pair of electrodes, a collector electrode adjacent said repeller electrode on the side thereof remote from said ionization chamber and an output means connected to said collector electrode.

References Cited in the le of this patent UNITED STATES PATENTS 2,712,097 Auwarter June 28, 1955 

